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New Scientist Live

Lost world hints at life in the Mesozoic

By Wendy Zukerman

IN AN echo of Arthur Conan Doyle’s famous book, a lost world containing a community of animals that has changed little since Tyrannosaurus and Triceratops walked the Earth has been found. But while Conan Doyle’s lost world was on a South American plateau, its real life equivalent lies on a submerged mountain off the Antarctic coast.

Rather than dinosaurs, this lost world is filled with crinoids, the stalked cousins of sea stars and sea urchins. Also known as sea lilies, crinoids were abundant in the shallow seas of the Mesozoic, 250 to 65 million years ago. Today, however, they were only thought to exist in small numbers in the deep sea, possibly because of pressure from recently evolved predators.

David Bowden at the National Institute of Water and Atmospheric Research in Auckland, New Zealand, and colleagues discovered over 1000 crinoids belonging to an as yet undescribed species on Admiralty seamount (see map) during an International Polar Year Census of Antarctic Marine Life voyage. “We were surprised to find such extensive populations,” he says.

The biologists also surveyed the neighbouring Scott Island seamount, but intriguingly they spotted only 22 crinoids there (Deep-Sea Research Part II, DOI&colon; 10.1016/j.dsr2.2010.09.006).

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The crinoids might have survived on Admiralty seamount because it is bathed in nutrient-poor waters from the Antarctic coast, which generally produce too little food to sustain predators, Bowden says. In contrast, Scott Island is influenced by nutrient-rich waters from the north, and predators are more common.

The accumulation of crinoid skeletons at Admiralty seamount suggests this community may have been thriving for around 25,000 years, says Bowden. Skeletal samples taken from the site could not be accurately carbon dated, so the team now plans to date rock samples to establish its age.

Although the community appears to be relatively young, the creatures seem so similar to their Mesozoic ancestors that the way they feed and position themselves to form a community is probably unchanged, says Tim O’Hara at the Melbourne Museum, Australia. “This way of life has been extinguished from most of the sea,” he says. “Now we can see it in all of its glory.”

“It’s extraordinary that they survived,” says Charles Messing at Nova Southeastern University Oceanographic Center in Florida, who was not involved in the study. “It’s just wonderful. When I first saw those pictures I thought&colon; when do we go back?”